On Planet GJ1214 B, Expect Exotic Cloud Cover

In recent years, scientists have discovered around a thousand planets orbiting other distant stars, including some called super-Earths. These planets are bigger than our rocky hole but smaller than any of our solar system's gas giants. Not much is known about these mysterious worlds.

NPR is Nell Greenfieldboyce reports on new evidence that one super-Earth is shrouded in clouds.

NELL GREENFIELDBOYCE, BYLINE: The super-Earth is called GJ1214 B. It's about two and a half times the size of the Earth, and every 38 hours it orbits a small star that's about 40 light years away. In an astronomical sense, that's right nearby.

LAURA KREIDBERG: But in an absolute sense it's still mind-bogglingly far. It's over 100 trillion miles away.

GREENFIELDBOYCE: Laura Kreidberg is at the University of Chicago. She says ever since this super-Earth was discovered, people have used the biggest and best telescopes to try to learn what its atmosphere is made.

KREIDBERG: We have basically thrown the kitchen sink at this planet. Up until this point it's really eluded our efforts to characterize it.

GREENFIELDBOYCE: She led a team that used the Hubble space telescope to make the most precise measurement of the atmosphere yet. They watched as the super-Earth repeatedly crossed in front of its star, so that they could analyze the star light that filtered through its atmosphere. What they saw suggests that this world is covered with clouds. But not clouds like the ones in our sky.

KREIDBERG: These clouds are probably something much more exotic. It could be, at the temperatures and pressures we see in the atmosphere, we'd expect clouds that could be made out of potassium chloride or zinc sulfide.

GREENFIELDBOYCE: Or maybe haze of soot.

The results are reported in the latest issue of the journal Nature. Kreidberg says new, more powerful telescopes are in the works. They should help scientists figure out what lies beneath these clouds.